Process of producing halftone mask negatives



Jan. 18, 1944. A. L HUTTKAY PROCESS PRODUCING HALF-TONE MASK NEGATIVES Original Filed. March 6, 1942 INVENTQR Patented Jan. 18, 1944 UNITED s'rA'rE PROCESS OF PRODUCING HAIFIONE MASK NEGATIVES i Arthur L. Huttkay, Newark, N. J.

Original application March 6. 1942, Serial No.

433,531. Divided-and this application Deeem bet 1, 1942', Serial No. 487,492.

ruary 9, 1942 18 Claim. (Cl. 95-5) This application is a division of U.' S. patent application Ser. No. 433,531, flied March 6, 1942.

This invention relates to new andimproved processes of preparing mask negatives, i. e., negatives which have'substantially opaque areas corresponding to the high-light sections and substantially transparent areas corresponding to the tone sections of an original drawing. Mask negatives of this type may be used for various purposes but one of the most important is their use in processesof preparing printingplates and more particularly in processes of eliminating half-tone screening dots in the high-light sections of half-tone positives or negatives.

An object of the present invention is to provide simple processes of preparing such mask negatives which processes are free from inexpedient methods such as laborious hand painting or hand opaquing.

Another object of this invention is to provide processes which will practically exclude the nethe line sections entirely transparent or white.-

''.in the someway, the term positive" designates photographic reproductiononany kind of photo- In Canada Febsections more or less transparent or white, and

graphic material, 1. e., on photographic-paper, film or plate, in which the high-light sections of the original drawing are substantially white or transparent, the tone values of the tone sections substantially the same as on the originaldrawing, and the line sections entirely opaque. It is evident that it in'the specification and cessity of using skilled labor for producing such mask negatives and which will greatly facilitate the necessary manipulation connected with pro ducing such negatives.

With the above objects in view, the present invention mainly consists in producing mask negatives by treating the entire surface of a con'-. tinuous tone negative made from'the original drawing with a preferably subtractive photographic reducer in the manner described in .detail below. In case the original drawing also contains line sections, the areas of the mask negative corresponding to these line sectionsshould' be transparent too. i

It should be noted that throughout thir lpe ch' ilcation and claims, the term ,high light sections is usedto designate those sections. of. an illustration or drawing which are'required to be printed in reproduction as pure white, i. e.,free from screen pattern, and is usually used as refersuperimposed negatives are mentioned, these negatives must consist of a photographic light-v sensitive layer on a transparent base. as for instance photographic films'or plates. l

Finally, it should be noted that the term we... ing as used throughout the specification and claims, should not be limited to the exact meaning of the word drawing, but that thiatermshould also comprehend'other illustrations, e. 3., photographic or like illustrations if these combined with a white background. Furthermore, it should be stressed that the term dz-awning as used throughout the specification andclaims' isintended to comprehend not only entire illustrations, but also part; thereof if the same'contain highlight: and tone section's, Thus, for in- -stance, also'a part oi a combined illustration 1 which in 'itseli consists of high-light andtone' sections. a. g., contains a tone section surrounded bywh'ite backgroundis considered-a drawing in accordance with the prosentinvontion also if the illustration contains othertone or high-light sec- 1 tions spaced from the aforementioned tone section, W

- Accordingly, the term "entire surface as used in the following description and claims is intended to define-the entire suriace of a drawing ring to background or "white" sections of an.-

illustration. The term tone sections" refers to the shadedor dark section of theoriginalillustration or drawing to be printed in reproduc-' tion as half-tones. The term "line sections" refers to the continuous opaque lines appearing on the original drawing.

Furthermore, it should be noted the negative" is used throughout the specification and claims to designate photographic reproductions on any typ of photographic material in a which the highlight sections-of theoriginal il-f lustrations or drawing appear opaque'the tone duced' from such a drawing.

The novel features which are considered as characteristic tor the present invention are set forth in particular in the appended claims. The

' cific embodiments, when read in connection with from the original drawing "shown in i, a

having highlight and tone sections;

oithe type defined in the or the entire surface of a negative or-positive proinvention itself, however,-together with addition- 1 objects and advantages thereof, will be best understood from the following description of spe- Figure 3 represents 'a oontinuous tone negadrawing shown in Figure 6 having high-light,

tone and line sections;

Figure 8 represents a continuous tone negative made from the original drawing shown in Figure 6;

Figure 9 shows a mask negative made from the continuous tone negative shown in Figure 8;

Figure 10 shows a drop-out half-tone and line positive made preferably with the aid of the mask shown in Figure 9 from the original drawing shown in Figure 6;

Figure 11 is a partly-opaque continuous tone negative according to Figure 8 having opaque areas corresponding to the line sections of the original drawing shown in Figure 6;

Figure 12 is a partly opaque continuous tone negative according to Figure 8 having opaque areas corresponding to the tone sections of the original drawing shown in Figure 6; V

Figure 13 is apartly opaque mask negative according to Figure 9 having opaque areascorresponding to the line sections of the original drawing shown in Figure 6; I g

Figure 14 is apartly opaque mask negative according to Figure '9 having opaque areas-corresponding to the tone sections of the original drawing shown in Figure 6;

Figure 15 is a partly opaque half-tone nega tive according-to Figure 7' having opaque areas corresponding to the line sections of the original drawing shown in Figure 6;

Figure 16 is a combined half-tone and line negative havingtransparent areas corresponding to the line sections of the original drawing shown in Figure 6; and i Figure 17 represents a half-tone screen of usual type used in connection with the processes described below in detaiL- J In order to facilitate understanding of the above-enumerated figures, it should be noted that in these figures all white areas representwhite high-light sections in the original drawings and white or transparent areas in thephotographic positives and negatives; all opaque areas in the 55 change of color of the intensified opaque areas of the mask negative; thus, for instance, by using certain combinations of bleaching and intensityfigures represent lin sections in the, original drawings and opaque areas inthe photographicv negativesand positives; all areas indicated in. the figures by diagonal shading represent tone sections of the original drawings and correspond-j ing areas of the negatives and positives; alldotted areas in the figures represent half-tone areas,

of the negatives and positives; 'and finally all areas indicated by horizontal shading represent, I

areas of the positives and negatives-made-opaque by painting out, i. e.,-coating with an opaque substance.

The above explanation will make the drawings of the present application so clear and .easily understandable for everybody skilled in this art that further elaborate description of each figure in detail may be omitted.

As already stated above, the mostimportant part of the present invention consists in a new process of producing a mask negative of the type shown in Figure 4 and in modifications of "1 entareas of this process. This mask negative should have such a distribution of density that (1) the completely white, i. e., high-light, sections of the original drawing shown in Figure 1 correspond to avery highldensity in the mask shown in Figure 4 while all tone sections of the original drawing should correspond to substantially transparent mask areas and that (2) there be substantially no difference oftone in the transpare mask. In order produce a mask negative meeting these requirements, this negative is produced by making first a continuous tone negative 3 of the a original drawing I, and then treating the entire surface of thisicontinuous tone negative 3 with a preferably subtractive photographic reducer until the tones in those areas of the negative which correspond to the tone sections of the original drawing substantially disappear; the thus 20 produced mask negative lis fixed, washed, and finally dried and used for producing a drop-out half -tone positive 5 in the. way described below in detail. This reducer treatment is preferably carried out while the continuous tone negative I is still wet. For reducing purposes,.any reducer of z the subtractive type may be used; such reducers have the characteristic feature that they reduce all densities of the developed imageby about the same density step regardless of the amount of density. Reducers of this type are,.for instance, ferricyanide combined with hypo,'a ferricyanide bleaching solution, an acid quinone solution, and ammonium persulfate in solutions free from halogen ions and others. I

Although very satisfactory results were obtained by thisnew reducing process, sometimes the opaque areas of the mask negative 4 became somewhat translucent; in order to avoid this, it

is herewith proposed to treat the continuous tone 40 negative 3 before or after the reducing step with a photographic intensifier. This photographic intensifying is preferably carried out after reducing and results in an intensification, i. e., darkening, of the opaque areas of the mask negative 4 without influencing the transparency of the transparent negativeareas. For this intensifying step, any known type of photographicintensifier may be used,-as for instance sulphide intenv sifiers, uranium intensifiers, methol silver inten- [5 sifiers, silver-hydroquinone intensifiers, and silver nitrate solutions having'a slow working reducing agent incorporated, therein.

The intensifying step described abovemay be combined with a bleaching step resulting in a from the photographic point of view, is about twice that of a dark grey negative.

of the present invention, the above-described 05 process of producing the mask negative of the type shown in Figure 4 is carried out in the following way:

First, from the original drawing l, a continuous tone negative is produced by photographing in the usual way, Then, the continuous tone negative 311s developed with a very short exposure time, e. g., one second at f-ll, and thereafter treated while still wet with a fairly strongsolution of potassium ferricyanide. This treatment 7 is continued until all areas of the negative which In accordancewith av preferred embodiment H this solution.

' opaque negative areas thus reduced mask negative A is ready for use.

- its high light a mask negative ther proceeding with finally placed in a mild-hypo,ni. e., thiosulphi I solution. After repeated washing and drying the mask negative isready for use. the potassium ierricyanide solution and the hypo bath separately and one after the other, it is also possible to make a solution containing a relatively high percentage'ot potassiumierricyanideand a smaller percentage of hypo developed continuous that of a process consisting of two separate treat? ment steps. Although it is possible to attain with a thus t eater I negatives! and s, and the mask negatives land 9 v Ilhe thus pro- 4 vInstead or using have been described above;

The hali-tonenegatives 2 and I, are madein on light-f sensitive photographic. material the original .drawing I and 6 respectively through the half:

the usual way, i. e., bylphotographing tone screen l1, and flashingfsi. e., photographing a white sheetor paper summon the samephotographic material.

and to treat the tone negative 3 only with The result will be the same as i tween the superimposed half-tone screen ll and arranged behind the 7 produced masknegative satisfactory results, it has been found thatintensiiyin'g otthe opaque mask areas is of advantage. This is carried out by again placing the mask negative produced in" the above described' way in a reducer, i. e., po-

tassium ierricyanide 'bath and bleaching the transparent; at this moment a slight image can be seen when the negative is he d against ablack background, Thereafter, without subjecting the opaque areas of the mask gives these areas abrownish red twice the photographic density of a I cordingto Figure 8 until they appear almost a negative to a hypo treatment, a sodium This intensifier intensiflesthe the dark grey areas before'intensifying. After 1 washing and drying the thus In some cases it proved intensified mask touch the original drawing before makingthecontinuous-tone negative, e. g., by lightesttones oi the tone sections and/or'making definite separation between'the lightest tones'of the tone. sections. and the high-light sections of the drawing. I

It would seem probable I 9 may be produced irom' the original drawing 6 having high-light, tone and line ctions without ducer resistant substance,- e.

darkening the .7 sections pure white, so asto have a I that a mask negative the above described way.- How 'during' reducing the attacked by the reducerythereby it is herewith pioposed to make then to coat described in A drop-outnhalf-tone positive of the type, i shown in Figure 5 is produced in accordance with the present invention by makingirom the the halitone negative 2 and the mask negativel, superimposing these nega-.

f sensitive material,

superimposing upon 'g., shellac, and therealter subject the thus partly coated continuous,

tone negative 8 to the reducer treatment described above in detail. coating dries and prevents the reducer from attacking the edges oi the line areas, resulting in a 9, with line areas equal to that of the original lines in drawing I.

For producing the 'ilnished drop-out positives or ,the type shown in Figures 5 and 10, other intermediatenegatives are also needed. In order not to crowd the detailed description of'the processes of producing the finished drop-out positives with unnecessary details, the methods or producins the intermediate negatives needed for these processes will be described below briefly before ,iur-

this description:

6O 1 This shellac *orother 3 having a width is photographed,

"I, with the soledifierence negative according areas corresponding original drawing 6 and-produced by painting out I the tone areasor the continuous tone negative 8. The partly opaque mask negatives l3 and, the] 1 first havingopaque areas correspondingto the line sections andthe latter having opaque areas correspondingtothe tone sections of the original drawings, are made negatives 2 and U The, combined ha1i tone and linenegative l6 is made in the same way'as the half-tone negative line sections of the original.-drawing,is placed bethe white sheet, or paper same. 1

Figures 11 to 15 show negatives beingfpartly v painted out, for the purposes I, ,of the present invention. Thus-Figure llshows a partly opaque continuous tone negative .ac-

having opaque areascorref r sponding to the line sectionsof the original draw} made by painting'out the line areas of the continuous tone negative 8. Fig- 7 y ure 12 shows a partlyopaque continuous tone to Fi ure, 8 having, opaque opaque, i.. e.,, partly ing 6; this negative is to the tone sections ,oithe negative is, in the way described in, connection with negatives H and 12.;

the line areas or the half-tone negative I, 1

the new processes of producing the finished drop-out positives will be the following indetail:

original, drawing l, tives iiponvan unexposed,photographic, lightphotographic material through the superimposed thereafter, the thus produced drop-out half-tone positive-is developed, fixed, and washed, and flnally dried. This drop-out halI-tonepositlve. 5 may also be produced by. unexposed light-sensi negative 3 h the unex an tive material, the continuous tone and'the mask negative 4 and exposing posed light-sensitive material through these superimposed negatives ,3 and 4 and the half tone screen I] arranged at a certain distance from these negatives, obtaining thereby the required 3 drop-out-hali-tone positive 5.

I It is evident that described below in which an original drawing or an material exposed this screen has to be arranged at a certain distance from the light-sensitive materialunto' which the photograph orprint is made; this distance varies-in accordance with; the A screen used well-known n and the method of its computation is to everybody skilled in this art and therefore does not have tobe explainedindetail. I

through the same being 'that during flash- 1 ing a transparent sheet of celiuloid or like material, having opaque areas corresponding to the bypainting out the mask a The partly opaque, I half-tone negative I5 is produced by painting out and-exposingthis unexposed Y in this case and in all cases uneiiposed photographic I through Qhali-tone screen l1, 1

4 assess:

shown in Figure 4, superimposing on an unexposed light-sensitive material the negatives l and II and exposing'the photographic material throughthese superimposed negatives, removing these negatives, superimposing on the thus part ly e posed photographic material the negative l2 and then exposing the photographic material through this 'negativeythe drop-out'half-tone and line positive ll obtained by this method is ,then developed, fixed, washed, and finally dried. Instead of the partly opaquehalf-tone negative i I, the partly opaque continuous tone negative I! may be used: in this case, however, in-

stead of the negatives l and II, the negatives. I

and II' are superimposed on the unexposed light-sensitive material and the photographic material is .then exposed through these superimposed negatives 4 and II and a half-tone screen'l'i arranged at a'eartain distance from the same. I

A preferred method'of producing a drop-out half-tone and line positive of the type shown in Figure 10 from the original drawing shown in the original drawing on a photographic film or 1 plate, developing, fixing, and washing thereafter the exposed film or plate, treating the entire surface of the thus produced continuous tone nega- 5 tive while still wet with a photographic reducer until the tones in those areas of the negative which correspond-to the tone sections of the orig inal drawing substantially disappear, fixing, washing, and finally drying the thus produced mask negative.

3. A process of producing from an original drawing having high-light and tone sections a photographic mask, negative oi thetype de- 1 scribed, comprising the steps of making a continuous tone negative of the original drawing,

treating thejentire surface of said continuous tone negative with a subtractive photographic reducer until the tones in those areas of the negative which correspond to the tone sections of the original drawing substantially disappear, fixing Figured, comprises the steps of making from 3 this drawing I two negatives, nanielya combined negative II and ahalf-tone and line mask negapcrimposing said negatives I and lion an unexposed light-sensitive photographic material, exposing said photographic material through said superimposed negatives 9 and I8, fixing, washing, and finally drying the thus produced drop-out half-tone and line positive Ill;

It should be stressed that the use of the mask negativesshown in Figures-4 and 9 and the above described new methods for producing tive l in the way described above in detail, su-

which correspond t the thus produced mask negative, and photo-, graphicallyintensifying said negative before or :after said reducing and fixing, increasing thereby the opacity of those areas of the negative which I correspond to the high-light sections of the original drawing.

4. A process of producing from an original drawing having high-light and tone sections a photographic mask negative of the type described, comprising the steps of making a continuous tone negative of the original drawing, treating the entire surface of said continuous tone negative with a subtractive photographic reducer until the tones in those areas of the negative the tone sections of the original drawing subs ntially disappear, fixing the thus produced mask negative, bleaching said negative, and intensifying the same consecutively without intermediate photographic fixing, said 40 bleaching and consecutive intensifying being carthese masks are not limited to processes of pro-- ducingfdrop-out half-tone positives and negatives in the wayidescribed above; these latter processes are described in detail only for the purpose of showing apreferred use of mask negatives produced in accordance with the present invention. These mask negatives may, how'- ever, be used also for various other purposes,-

such as for instance for combining drawn and photographed cinematographic and photographried out before or after said photographic reducing and fixing of said negative and resulting in increase of the opacity of those areas of the negative which-correspond to the high-light sections of the original drawing.

5. A process of producing from an original ,awing'having high-light and tone sections a photographic mask negative of the type described, comprising the steps of making a conso tinuous tonenegative of the original drawing,

ic pictures, for purposes ofbackground photog- 'fraphy or cinematography, and thelike. Therefore, these mask negatives and the above-described processes oi producing. the same are claimed not only in combination with and for treating the entire surface of said continuous tone negative with a subtractivephotographic reducer until the tones in those areas of the negative which correspond to the tone sections of the original. drawing substantially disappear and the purposes of producing printing plates, but

' in general for any purposes whatsoever.

What is claimed as newis' 1. A process cit-producing {roman original drawing havins high-light tone sections a photographic'mask negative the type described, comprising the stepsof making a continuous tone negativeof the original treat- 1818 the entire samce ofsaid"continuous tone negative is a photographic reducer until the these areas are becoming substantially transparent, fixing. andwashing the thus produced masknegative, hereafter bleaching said mask negative by means of a photographic subtractive reducer until also the opaque areas of the negatones in thos'e, of'the negative which correspend to-thetone-s'ections of the original draw: ing substantially disappean-andfixing the thus produced mask negative thereafter.

2. A- process of producinggfrom an original drawing having high-light "and tone sections a photographic mask negative of the type detive which correspond to the high-light sections of the originaldrawing are becoming substantially, transparent, and intensifying the thus treated mask negative without intermediate fixto the tonesections of the inf-iginal drawing remain substantially transparent.

6. A process of producing from an original drawinghaving high-lightand tone sections a photographic mask negative of the type described, comprising drawing in' such a manner as to have a definite d. e man or photogra hin 76 amnion between the lightest tones of the tone ing, thereby attaining strong opacity in the areas. corresponding to the vhigh-light sections of the original drawing, while areas, corresponding retouching the Original dium sulphidesolution without intermediate ,fix ing, thereby attaining strong opacity in the areas corresponding to the :highelight sections of the original drawingywhile thexareas corresponding sections, and thehigh-iight sections a the drawing, photographing the thus retouched drawing on a photographic film orplate, developing, fix

ing, and washing thereafter the exposed film or plate, treating the entire surface of the thus pro- I ducedflcontinuous ton negative while; still wet with a subtractivephotographic reducer until the tones in those areas of the negativewhich corree:

spond to the tone sections of the original drawing substantially disappear, fixing, washing, and finally drying the thus produced masknegative.

'7. A process of producing from" .an original drawing having high-light and tone sections a ,negative of the original drawing, reducing the I photographic mask negative of the type described, comprisingv the steps of photographing the original drawing on a photographic film orplate, developing, fixing, and washing thereafter the exposed film or plate, treating the. entire surface of the thus produced continuous tone negative whilev still wet'with a fairly strong solution of potassium ferricyanide until the tones in those areas of the negative whichcorrespond to the tone sections of, the original drawing substantial 1y disappear, fixing',,washing, and finally drying the thus produced mask negative. a

8. A- process of producing from ,an original drawing having high-light, and tone sections a photographic mask negative of the type described,

comprising the steps of photographing the origi-' nal drawing on a photographic-minor plate,

developing, fixing, and washing thereafter the exposedfilm or plate, treating the entire surface of the thus produced continuous tone negative while still wet with a fairly,strong-solution of potassium ferricyanide until the tones in those areas or the negative which correspond to the tone sections of the originaldrawing substantially disappear, fixing the, thus reduced negative with a thiosulphite solution, washing, and 1 finally drying the thus producedmask negative. 9. A process of producing from an original drawing having high-light and tonesectionsa photographic mask negativeof the type described.

tone negative of the original drawing, treating the entire surface of said continuous tone negative with a subtractive photographic reducer until the tones in those areas of the negative which correspond to the tone sections of the original drawing substantially disappear and these areas are becoming substantially transparent, fixing and washing the thus produced mask negative, hereafter treating said mask negative with a po: tassium ferricyanide solution, and intensifying the thus treated mask negative without intercomprising the steps of making a continuous 1 mediate fixing, thereby attaining strong opacity v in the areas corresponding to th high-light sections of the original drawing, while the areas corresponding to the tone sections of the original drawing remain substantially transparent.

10. A process of producing from an original drawing having high-lightand tone sections a photographic mask negative of the type described, comprising the steps of making a continuous tone negative of the original drawing, treating the entire surface of said continuous tone negative with a subtractive photographic reducer un: til the tones in those areas of the negative which tions of the continuous correspond to the tone sections of the original i drawing substantially disappear and these areas are becoming substantially transparent, fixing andwashing the thus produced mask negative, hereafter treating said mask negative with a potassium ferricyanide solution, and intensifying the thus treated mask negative with a somain substantiallytransparent. 11. A, process; of prancing from an ;-original drawing having -.high -l ight and tone sections a photographicmask negative of the-type described,

comprising the steps ofinakinga continuous tone entire surface of: said continuous ton negative with a fairly-strong solution of potassium ferri cyanide, fixing the thus treatednegativ with a thiosulphite solution,- washing the same, hereafter treating. the thus producednegative with a substantially saturated solution of potassium ierricy'anide, and intensifying thereafter the thus treated negative with a s'odiumsuiphide solu-;

tion without intermediate fixing, obtaining there-' ,by a mask negative being strongly opaque in the areas corresponding to they high-light sections of theoriginal drawing, while the areas:-corresponding to the tone sections of the original drawing remainsubstantially transparent.

12. A process of producing from an original drawing having highelight and tone-section a photographic mask negative or the type described, comprising the stepsPfretouching said drawing.

in such a manner as to1have= a definitesepara- I tion between the lightest tones of thetone-sec tions, and the high-light sections of th draw ing, makinga continuous tone, negative from first with a fairly strong solution of potassium thus produced negative with a substantially sat-,- u'rated solution of intensifying-thereafter the thus treated negative with a sodium sulphide solution withoutjintermediate'fixing, obtaining thereby a masknega tive being strongly opaque in the areasycorrev spending. tothe'high-light sections of the original drawing, while. the areas corresponding to the tone sectionsof the original drawing remain substantially transparent.

13. Aprocess of producing a. mask negative of the type described from an original drawin having high-light, tone, and line sections, comprising making a continuous tone negative from said drawing, coating those portions of the continuous tone negative which correspond to theline sections of the original drawing with a transparent reducer-resistant coating material, photographically reducing the thus treated continuous tonenegative until the tones in those areas of the negative which correspond to. the tone sections of the original drawing substantially disappear, and fixing the thus produced mask negative thereafter.

14. Aprocess of producing a mask negative of the type described from an original drawing having high-light, tone, and line sections, comprising thesteps of making a continuous tone negative from said drawing, coating those portone negative which correspond to the line sections of the original drawing with transparent shellac, photographically reducing the entire surface of the thus treated continuous tone negative until the tones in those areas of. the negative which correspond to the,

tone sections of the original drawing substantially disappear and these are becomingsubto the tone sections of the original drawing-rev the thus retouched original drawing treating the entire surface of said-continuous tone negative ferricyanide and then with a thiosulphite solution, washing the same, hereafter treating rthe potassium ferricyanide, and

the entire surface of stantially. transparent-"fixing andv washing thethus producedmask-inegative, hereafter bleaching said half-tone-mask negative by means 01' a photographic subtractive reducer until also the opaque areas of the negative which correspond to the high-light sectionsof the original drawing are becoming substantially transparent, and

intensifying thethus treated mask negative without intermediate fixing; thereby attaining strongtopacity .in the areas corresponding to the high-light sections of the original drawing,"

while the areas corresponding to the tone and line sections ,oi'the original drawing remain substantially transparent.

15. A process of producing a mask negative 01' the type described from, an original drawing, having high-light, tone, and line sections, comthe steps or making a continuous tone negative lrom saiddrawing, coating those por'-' tions;.-ot=the"..continuous tone negative which to the-line sections or the original drawing with 'a' transparent reducer-resistant a' ia'irly' solution oibpotassium terricyanide-fixing the. thus treated negative with a thiosulphite' solutiomwashing the same, herealter treating the thus produced negative with reducing theentire surface of a the'thu's treatedeontinuous tone negative with the thus retouched original drawing, coating those portions of said continuous tone negative which'correspond 'to'line sections of the original drawing with shellac, treating the entire-surface of the thus partly coated continuous tone negative first with a fairly strong solution of potas-' sium .ferricyanide and then with a thiosulphite solution, washing thezsame, hereafter ,treating the thus produced negative with a substantially saturated solution of potassium ferricyanide, and-intensifying thereafter the thus treated negative with a sodium sulphideisolution without intermediate vfixing, obtaining thereby a mask negative being strongly opaque in the areas corresponding to, the high-light sections of the original drawing, while the areas a substantially saturated solution otpotassium rerric'y'anide;- ma intensiiying thereafter. the thus treated negative with a sodium sulphide solution without intermediate fixing, obtaining therebya mask negative being strongly opaque in the areas correspondingto the high-light sections of theoriginal drawing. while the areas corresponding to the tone and line sections of the original transparent.

16.1 process of producing from an original drawing having high-light' and tone sectionsa drawing remain substantially I correspondl ngto the'tone and-line sections of the original drawing remain substantially transparent.

'17. A process of producing from'an original I drawing having high-light and tone sections a photographic mask negative of the type described, comprising the steps of making a continuous tone negative'of the original drawing, chemically treating the entire surface of said continuous tone negative until the tones in those areas of the negative which correspond to the tone sections of the original drawing substantiallydisappear, and fixing the thus produced mask negative thereafter.

18. A process'of producing from an original drawing having high-light and tone sections a I photographic 'mask negative of the type described, comprising the steps of making a continuous tone= negative of the original drawing,

cheinically treating the entire surface oi said continuous tone negative until the tones in those areas of the negative which correspond to the tone sections of the original drawing substanphotographic mask negative or the type'described,comprising the steps of retouching said 4 drawing in such a manner as to have a definite separation between the lightest tones oi the tone sections'and thehigh-light'sections oi the drawing, making a continuous tone negative from tially disappear, fixing the thus produced mask negative; and photographically intensifying said negative, increasing thereby the opacity of those areas of the negative which'correspond to the high-light sections of the original drawing. 

